In positive control of several sugar-metabolism-related operons, the catabolite activator protein (CAP) binds to DNA to stimulate transcription. What causes an increase in CAP binding?

A. decrease in glucose and decrease in repressor

B. decrease in glucose and increase in cAMP

C. decrease in glucose and increase in repressor

D. increase in glucose and decrease in cAMP Reply Quote Email Author

The correct answer is option B. "decrease in glucose and increase in cAMP".

Explanation:

The catabolite activator protein (CAP) is a DNA binding protein that regulates the transcription of many genes involved in the metabolism of different sugars. CAP is one regulator of the lac operon, a series of connected genes responsible of lactose metabolism. An increase in CAP binding results in the activation of the lac operon, which takes place by a decrease in glucose and increase in cyclic AMP (cAMP). Low levels of glucose stimulate CAP and allows that glucose is obtained from lactose metabolism. cAMP is a "hunger signal", the more cAMP is present the more the cell needs glucose.